Partial Fraction Expansion: residued.m

Figure H.9 gives a listing of a matlab function for computing a ``right justified'' partial fraction expansion (PFE) of an IIR digital filter $H(z)=B(z)/A(z)$ as described in §6.8 (and below).

The code in Fig.H.9 was written to work in Octave, and also in Matlab if the 'm' argument is omitted (in two places).

Figure H.9: Matlab/Octave function for computing the group delay of a digital filter.

 

function [r, p, f, e] = residued(b, a, toler)
if nargin<3, toler=0.001; end
NUM = b(:)';
DEN = a(:)';
nb = length(NUM);
na = length(DEN);
f = [];
if na<=nb
  f = filter(NUM,DEN,[1,zeros(nb-na)]);
  NUM = NUM - conv(DEN,f);
  NUM = NUM(nb-na+2:end);
end
[r,p,f2,e] = residuez(NUM,DEN,toler);